Construction of interconnected acidity functions based on ortho substituted anilines and N-methylanilines as indicators

Article abstract of DOI:10.1135/cccc20011638

The log I values of 15 mainly ortho substituted derivatives of aniline and N-methylaniline have been measured spectrophotometrically in sulfuric, perchloric, and methanesulfonic acids. A new algorithm has been suggested for construction of acidity functions enabling simultaneous and independent construction of acidity functions in various media under the condition of equal values of pK_a of the same indicators in the given media. The so-called interconnected acidity functions have been constructed with using this algorithm and the log I values measured in the above media, and the pK_a values have been calculated. The resulting acidity functions and pK_a values agree well with the corresponding literature data.

Full text of DOI:10.1135/cccc20011638

1638
Pytela, Kulhánek, Jirásková, Nevěčná:
CONSTRUCTION OF INTERCONNECTED ACIDITY FUNCTIONS
BASED ON ortho SUBSTITUTED ANILINES AND N-METHYLANILINES
AS INDICATORS
b1
b2
Oldřich PYTELAa1,*, Jiří KULHÁNEKa2, Eva JIRÁSKOVÁ and Taꢀjana NEVĚČNÁ
a
Department of Organic Chemistry, University of Pardubice, 532 10 Pardubice,
Czech Republic; e-mail: oldrich.pytela@upce.cz, jiri.kulhanek@upce.cz
Department of Inorganic and Physical Chemistry, Palacký University Olomouc, 771 46 Olomouc,
Czech Republic; e-mail: jiraskova@prfnw.upol.cz, nevecna@prfnw.upol.cz
1
2
b
1
2
Received May 28, 2001
Accepted Novem ber 12, 2001
Th e log I values of 15 m ain ly ortho substituted derivatives of an ilin e an d N-m eth ylan ilin e
h ave been m easured spectroph otom etrically in sulfuric, perch loric, an d m eth an esulfon ic
acids. A n ew algorith m h as been suggested for con struction of acidity fun ction s en ablin g si-
m ultan eous an d in depen den t con struction of acidity fun ction s in various m edia un der th e
con dition of equal values of pKa of th e sam e in dicators in th e given m edia. Th e so-called in -
tercon n ected acidity fun ction s h ave been con structed with usin g th is algorith m an d th e
log I values m easured in th e above m edia, an d th e pKa values h ave been calculated. Th e re-
sultin g acidity fun ction s an d pKa values agree well with th e correspon din g literature data.
Keyw ord s: Acidity fun ction s; Basicity; Am in es; An ilin es; N-Meth ylan ilin es; ortho-Effect;
Substituen t effects.
Th e determ in ation of dissociation con stan ts of weak bases by m ean s of con -
struction of acidity fun ction s1,2 is on e of com m on ly adopted procedures.
Th e form al defin ition of acidity fun ction H as a differen ce between th e pKa
value of an in dicator (weak base) an d logarith m of th e con cen tration ratio
of its proton ated an d n on proton ated form s, log I, at a given con cen tration
of th e proton atin g acid is quite sim ple (Eq. (1)).
H = pKa – log I
(1)
Th e ph ysico-ch em ical in terpretation of acidity fun ction as a fun ction of
con cen tration of th e proton atin g acid (an d/or its com pon en ts3) an d th e in -
dicator used is far m ore com plicated2,4–19. Neverth eless, given a series of
in dicators fulfillin g certain con dition s (e.g. refs2,4), it is possible to experi-
m en tally obtain th e I values of Eq. (1) an d con struct th e acidity fun ction as
Collect. Czech. Chem. Commun. (Vol. 66) (2001)
doi:10.1135/cccc20011638

Interconnected Acidity Functions
1639
a fun ction of con cen tration of th e respective acid (for a survey of algo-
rith m s, see, e.g., ref.20). Subsequen tly, with h elp of Eq. (1), it is possible to
calculate th e pKa values of th e used in dicators from th e acidity fun ction ob-
tain ed an d th e experim en tal log I values. Th e pKa values can also be deter-
m in ed, with out con structin g th e acidity fun ction , usin g th e gen eralised
acidity fun ction s (excess acidity6) based on th e sim ilarity prin ciple (Bun n ett
an d Olsen 7, Marzian o et al.8–16, Cox et al.17–19). However, th e pKa values
evaluated by various procedures differ, th e differen ces bein g as h igh as in
un its6,21–23. Th e classic way of calculation of dissociation con stan ts usin g of
con struction of th e respective acidity fun ction is probably m ore suitable for
series of in dicators of th e sam e or sim ilar ch em ical structures. Th is is particu-
larly true with respect to a closer fit between th e experim en tal log I values
an d th e con structed acidity fun ction in th e respective con cen tration in ter-
val. Th e procedure h as a drawback in th e fact th at th e acidity fun ction is
con structed per partes with possible cum ulated error for h igh er con cen tra-
tion s of acid. Th is drawback is n ot en coun tered in a procedure usin g th e ex-
cess acidity fun ction s6,8–19, wh ich is m ore gen eral an d easier for calculation .
An advan tage is th e possibility of obtain in g in dividual pKa values of weak
bases wh ereas a drawback is a poten tially less close fit of th e depen den ce of
log I on th e values of th e gen eralised acidity fun ction because of specific
properties of th e system m easured.
An oth er com plicatin g factor is th e depen den ce of th e pKa values of weak
bases on th e proton atin g acid in th e given m edium . In spite of th e fact th at
accordin g to its th erm odyn am ic defin ition th e pKa value sh ould be in de-
pen den t of th e acid used, th e resultin g values differ – som etim es even quite
substan tially – due to experim en tal m eth od an d th e above-m en tion ed way
of evaluation 8,11,13,16,22,24,25. Th e correctn ess of th e pKa values obtain ed by
m ean s of various acidity fun ction s can th us be h ard to com pare, an d th e
process of takin g th e average value of data from differen t sources n eeds n ot
always represen t th e best solution . Th e results obtain ed usually can n ot be
adopted in furth er in terpretation , e.g., in studies of effect of structure upon
dissociation by m ean s of correlation relation sh ips. It can be expected th at a
pKa value in depen den t of th e acid used will be accessible by m easurem en ts
in a series of differen t acids with th e presum ption th at suitable processin g
of experim en tal data will allow elim in ation of specific properties of th e
acids. Th e resultin g acidity fun ction s defin ed for a given series of in dicators
will th en fulfil th e above-given con dition viz. th ey will provide th e pKa val-
ues in depen den t of th e acid used. Such presum ption h as n ot been form u-
lated an d th e correspon din g calculation procedure h as n ot been suggested
yet.
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Pytela, Kulhánek, Jirásková, Nevěčná:
Th e aim of th is paper is to suggest an d verify th e n ew calculation algo-
rith m for th e pKa values in depen den t of m edium by m ean s of con structin g
specific acidity fun ction s referred to as “in tercon n ected acidity fun ction s”.
For verification of th e procedure suggested, we h ave ch osen suitable (pre-
dom in an tly ortho) substituted an ilin es an d N-m eth ylan ilin es an d th e m edia
of sulfuric, perch loric an d m eth an esulfon ic acids. Th e calculation also in -
cludes th e experim en tal values of log I obtain ed in th e previous work27
wh ich on ly dealt with th e dissociation con stan ts of ortho substituted an i-
lin es in perch loric acid.
THEORETICAL AND CALCULATIONS
Wh en evaluatin g pKa values of weak bases in stron gly acidic m edia, on e al-
ways works with th e sam e set of th ree quan tities. Th e first is th e pKa value,
wh ich is a fun ction of th e in dicator (weak base), tem perature an d m edium .
Both th e in dicator an d tem perature are defin ed un am biguously, wh ile th e
properties of m edium con tin uously ch an ge with ch an gin g con cen tration of
th e stron g proton atin g acid. In order to approach th e th erm odyn am ic con -
ception of dissociation con stan t as close as possible, it is advisable to defin e
it in such a way as to depen d on th e solven t used (m ost often water) but
n ot on th e acid used an d its con cen tration . Th is approach h as been
adopted in th e presen t paper. Th e secon d quan tity is th e ratio of th e
proton ated an d n on proton ated form s of th e in dicator referred to as I. Th is
quan tity depen ds on th e in dicator, th e proton atin g acid used an d its con -
cen tration . Th e last quan tity is a certain ch aracteristic of acidity of m edium
(th e acidity fun ction H or th e con cen tration of acid in com bin ation with
th e excess acidity fun ction ): th is quan tity depen ds on th e proton atin g acid
an d its con cen tration an d (in th e case of acidity fun ction ) also on th e in di-
cator. With regard to th e above-m en tion ed requirem en t of in depen den ce of
pKa value upon th e acid an d its con cen tration , th e ch aracteristic of acidity
of m edium m ust in clude th e activity coefficien ts of com pon en ts of m edium
as well as th ose of both form s of th e in dicator. From am on g th e quan tities
m en tion ed, experim en tally accessible is th e value of con cen tration ratio of
proton ated an d n on proton ated form s of in dicator (I or log I); also kn own
are th e type an d con cen tration of th e acid (or, as th e case m ay be, th e ex-
cess acidity fun ction for th e given acid too) an d, of course, th e in dicator
used.
If th e log I values of th e sam e in dicators m easured in various proton atin g
acids are available, th en it is possible – un der th e con dition of m edium -
in depen den ce of dissociation con stan t – to con struct sim ultan eously th e
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Interconnected Acidity Functions
1641
in dividual acidity fun ction s in all th e m edia by m ean s of th e iteration algo-
rith m described elsewh ere20. Th is algorith m was derived from Eq. (1) an d is
based on th ree operation s in each iteration step In th e first operation , th e
average of log I values of all th e in dicators is calculated for th e sam e con -
cen tration s of acid. Th is provides an acidity fun ction depen din g on con -
cen tration . Th e secon d operation con sists in calculatin g (for each in dicator)
th e average distan ces of log I values from th e acidity fun ction th us con -
structed, i.e. th e pKa values. In th e last operation , th e pKa values of each in -
dicator are ch an ged (sh ifted) by th e calculated pKa value an d used again in
th e first operation . Th e iteration calculation is fin ish ed if th e m axim um
ch an ge is sm aller th an a ch osen sm all n um ber. Th e described algorith m 20
h as been m odified in th e presen t work by in cludin g (in to th e secon d opera-
tion of each iteration step) th e procedure of takin g th e average of pKa val-
ues for th e sam e in dicator. Th ereby th e values of acidity fun ction s in th e
in dividual acids are in tercon n ected an d th e result is th e “boun d” acidity
fun ction s.
EXPERIMENTAL
Ch em icals
Th e syn th eses of 2,6-dich loroan ilin e, 2-n itroan ilin e, 2-m eth yl-6-n itroan ilin e, 4-ch loro-
2-n itroan ilin e, 2-ch loro-6-n itroan ilin e, 2,4-dich loro-6-n itroan ilin e, 2,4-din itroan ilin e, an d
2,6-din itroan ilin e were described in an earlier paper27. 2-Meth oxy-6-n itroan ilin e was syn th e-
sized28 in 48% yield by 6-h h eatin g of eth an olic solution of 1-m eth oxy-2,3-din itroben zen e28
with excess 20% aqueous am m on ia in a sealed am poule at 160 °C. A sim ilar procedure was
adopted for th e N-m eth yl derivative by usin g aqueous m eth ylam in e (yield 32%). 2,5-Di-
ch loro-4-n itroan ilin e was obtain ed29 in 52% yield by n itration of 2,5-dich loroacetan ilide
an d subsequen t h ydrolysis. N-Meth yl-2-n itroan ilin e an d N-m eth yl-4-n itroan ilin e were pre-
pared30 by 6-h h eatin g of eth an olic 1-ch loro-2-n itroben zen e an d 1-ch loro-4-n itroben zen e,
respectively, with m eth ylam in e in a sealed am poule at 130 °C (practical yields 60 an d 79%,
respectively). N-Meth yl-2-ch loro-6-n itroan ilin e was obtain ed31 in 65% yield by 15-h h eatin g
eth an olic 1,2-dich loro-3-n itroben zen e32 with m eth ylam in e in a sealed am poule at 150 °C.
N-Meth yl-2,6-din itroan ilin e was syn th esised in 42% yield by h eatin g 2-ch loro-1,3-din itro-
ben zen e with m eth ylam in e33
.
The synthesised derivatives were identified by m eans of NMR spectrom etry (360 MHz, Bruker).
Th eir purity was ch ecked by GC/MS an alysis (GCQ-tan dem , Fin n igan ). Th e oth er an ilin es
used were com m ercial products (Fluka Ch em ie AG). Before m easurem en ts, th e an ilin es were
purified by recrystallisation from eth an ol (2-NO2, 2-CH3-6-NO2, 2,4-diNO2, 2,6-diNO2,
N-CH3-4-NO2) or aqueous eth an ol (2-OCH3-6-NO2, N-CH3-2-NO2, N-CH3-2,6-diNO2).
2,5-Dich loro-4-n itroan ilin e was recrystallised from 50% acetic acid. Th e oth er an ilin es were
recrystallised from h exan e. Perch loric acid (Carlo Erba – Ch ím ica Milan o, pa.), sulfuric acid
(Lach em a Neratovice, pa.), m eth an esulfon ic acid (Sigm a–Aldrich ), sodium h ydroxide
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

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Pytela, Kulhánek, Jirásková, Nevěčná:
(Lach em a Neratovice, pa.), an d m eth an ol (Lach em a Neratovice, for UV) were used with out
purification .
Measurem en t of Con cen tration Ratio of Proton ated an d Non -Proton ated Form s
of In dicators
Th e m easurem en ts were carried out spectroph otom etrically usin g an SP 8-100 (Pye Un icam )
an d a DU 7500 (Beckm an ) apparatus. Exact con cen tration s of perch loric, sulfuric, an d
m eth an esulfon ic acids were determ in ed alkalim etrically. Th e con cen tration s of stock solu-
tion s of th e in dividual substituted an ilin es in m eth an ol were 10–1–10–2 m ol dm –3. From th e
stock solution s, 0.05 cm 3 was pipetted in 25-m l calibrated flasks, th ey were filled up to th e
m ark by addin g th e respective aqueous acid of suitable con cen tration , an d th e absorban ce
ch an ges depen din g on con cen tration of proton atin g acid were read at th e wavelen gth of th e
lon gest-wave m axim um . Som e m easurem en ts were repeated several tim es.
Con struction of Acidity Fun ction
Th e log I values were calculated from th e spectral data in usual way2. For th e con struction
of in tercon n ected acidity fun ction s usin g th e above-described algorith m , th e log I values of
substituted an ilin es in perch loric acid were adapted given in a previous paper27 alon g with
th e values of substituted an ilin es an d N-m eth ylan ilin es n ewly m easured in sulfuric,
perch loric an d m eth an esulfon ic acids (Tables I–III). As a stan dard in dicator, to wh ich th e
acidity fun ction s were fixed durin g calculation , we adopted 2-n itroan ilin e with pKa = –0.300
(ref.27). Th e suggested calculation algorith m was im plem en ted by m ean s of a program in
Delph i lan guage. Th e oth er calculation s were carried out by stan dard statistical algorith m s.
RESULTS AND DISCUSSION
Acidity Functions
Th e acidity fun ction s H0 in sulfuric, perch loric, an d m eth an esulfon ic acids
con structed by th e above-described algorith m from th e data given in previ-
ous paper20 an d in Tables I–III are presen ted in Table IV. Th e graph ical rep-
resen tation of depen den ce of H0 on th e acid con cen tration is in Fig. 1. Th e
residual stan dard deviation s = 0.064 calculated from th e differen ce be-
tween (pKa – log I) values an d H falls in a usual ran ge20
.
In order to verify th e correctn ess of adjustm en t of values of th e acidity
fun ction s an d h en ce also th e correctn ess of th e suggested algorith m , th e re-
sults were com pared with th e already publish ed H0 fun ction s in sulfuric
an d perch loric acids24,34 for th e con cen tration s given in Table IV. Th e de-
pen den ce obtain ed by regression for sulfuric acid34 is given by Eq. (2).
H0(H2SO4) = (0.028 ± 0.022) + (0.985 ± 0.006) H0(H2SO4, ref.34)
s = 0.11, r = 0.999, n = 69
(2)
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Interconnected Acidity Functions
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TABLE I
Values of log I depen din g on con cen tration of sulfuric acid in water for th e studied substi-
tuted derivatives of an ilin e of th e followin g gen eral form ula (th e substituen ts n ot sh own are
h ydrogen s)
NHR
X6
X5
X2
X4
Substituen tsa
X2 = X6 = Cl
c (log I)
0.0470 (–1.08), 0.0789 (–0.881), 0.114 (–0.533), 0.149 (–0.464),
0.168 (–0.3), 0.195 (–0.168), 0.243 (–0.04), 0.271 (0.014), 0.289
(–0.016), 0.336 (0.061), 0.424 (0.182), 0.516 (0.229), 0.585
(0.316), 0.681 (0.474), 0.784 (0.507), 0.875 (0.602), 1.02 (0.682),
1.52 (0.989), 2.06 (1.312)
X2 = NO2 (1)
0.243 (–0.833), 0.321 (–0.632), 0.377 (–0.621), 0.424 (–0.562),
0.516 (–0.306), 0.633 (–0.212), 0.731 (–0.203), 0.828 (–0.145),
1.02 (–0.006), 1.21 (0.128), 1.36 (0.214), 1.45 (0.27), 1.52
(0.297), 1.63 (0.377), 1.77 (0.412), 1.91 (0.468), 2.06 (0.559),
2.24 (0.749), 2.42 (0.776), 2.60 (0.841), 2.83 (0.979), 2.93
(1.081), 3.22 (1.138), 4.07 (1.523), 5.22 (2.165)
X2 = NO2 (2)
0.336 (–0.716), 0.516 (–0.478), 0.633 (–0.376), 0.731 (–0.249),
0.875 (–0.106), 1.06 (–0.049), 1.14 (0.036), 1.41 (0.172), 1.52
(0.261), 1.63 (0.32), 1.84 (0.416), 1.91 (0.461), 2.06 (0.508), 2.24
(0.661), 2.42 (0.747), 2.60 (0.874), 2.93 (1.002), 5.00 (2.196)
X2 = NO2 (3)
0.219 (–0.843), 0.336 (–0.652), 0.516 (–0.374), 0.633 (–0.299),
0.731 (–0.245), 0.875 (–0.098), 1.06 (0.003), 1.14 (0.077), 1.41
(0.22), 1.52 (0.281), 1.63 (0.315), 1.84 (0.447), 1.91 (0.491), 2.06
(0.545), 2.24 (0.688), 2.42 (0.775), 2.60 (0.831), 2.93 (1.02), 5.00
(2.293)
X2 = CH3O, X6 = NO2 (1) 0.336 (–0.75), 0.424 (–0.709), 0.516 (–0.596), 0.681 (–0.453),
0.784 (–0.372), 0.875 (–0.261), 1.02 (–0.224), 1.12 (–0.187), 1.36
(–0.073), 1.52 (0.071), 1.63 (0.142), 1.73 (0.184), 1.84 (0.247),
1.91 (0.257), 2.06 (0.322), 2.24 (0.465), 2.55 (0.628), 2.93 (0.888)
X2 = CH3O, X6 = NO2 (2) 0.321 (–0.869), 0.424 (–0.745), 0.516 (–0.56), 0.585 (–0.525),
0.681 (–0.456), 0.784 (–0.342), 0.828 (–0.327), 0.875 (–0.293),
1.02 (–0.223), 1.12 (–0.133), 1.25 (–0.087), 1.36 (–0.022), 1.45
(0.061), 1.52 (0.093), 1.63 (0.118), 1.69 (0.17), 1.73 (0.176), 1.77
(0.213), 1.89 (0.29), 1.92 (0.304), 2.06 (0.319), 2.12 (0.447), 2.24
(0.479), 2.47 (0.582), 2.55 (0.642), 2.93 (0.845)
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Pytela, Kulhánek, Jirásková, Nevěčná:
TABLE I
(Continued)
Substituen tsa
c (log I)
X2 = CH3, X6 = NO2
0.424 (–1.088), 0.516 (–0.911), 0.585 (–0.781), 0.681 (–0.716),
0.784 (–0.606), 0.828 (–0.597), 0.875 (–0.559), 1.02 (–0.487), 1.12
(–0.418), 1.25 (–0.322), 1.36 (–0.27), 1.45 (–0.115), 1.52 (–0.157),
1.63 (–0.089), 1.69 (–0.038), 1.73 (–0.044), 1.77 (0.024), 1.89
(0.066), 1.92 (0.129), 2.06 (0.157), 2.12 (0.238), 2.24 (0.223), 2.47
(0.38), 2.55 (0.392), 2.93 (0.594)
X2 = NO2, X4 = Cl (1)
X2 = NO2, X4 = Cl (2)
X2 = NO2, X4 = Cl (3)
X2 = NO2, X4 = Cl (4)
0.516 (–1.358), 0.784 (–0.979), 1.02 (–0.947), 1.21 (–0.646), 1.41
(–0.468), 1.58 (–0.398), 1.84 (–0.255), 2.06 (–0.146), 2.16 (–0.046),
2.39 (0.051), 2.53 (0.073), 2.72 (0.166), 2.88 (0.248), 2.93 (0.256),
3.22 (0.431), 3.44 (0.483)
0.516 (–1.225), 0.784 (–0.967), 1.02 (–0.839), 1.21 (–0.547), 1.41
(–0.531), 1.58 (–0.376), 1.84 (–0.177), 2.06 (–0.131), 2.16 (–0.094),
2.39 (–0.007), 2.53 (0.084), 2.72 (0.221), 2.88 (0.241), 2.93 (0.296),
3.22 (0.378)
1.02 (–0.82), 1.21 (–0.73), 1.41 (–0.65), 1.58 (–0.602), 1.73
(–0.521), 1.84 (–0.384), 2.06 (–0.312), 2.16 (–0.17), 2.39 (–0.087),
2.53 (–0.013), 2.72 (0.054), 2.88 (0.116), 2.93 (0.15), 3.22 (0.26),
3.44 (0.387)
0.516 (–1.236), 1.02 (–0.783), 1.21 (–0.71), 1.41 (–0.6), 1.58
(–0.547), 1.73 (–0.467), 1.84 (–0.359), 2.06 (–0.294), 2.16 (–0.145),
2.39 (–0.063), 2.53 (–0.028), 2.72 (0.093), 2.88 (0.134), 2.93
(0.163), 3.22 (0.306), 3.44 (0.402)
X2 = X5 = Cl, X4 = NO2 2.24 (–0.778), 2.47 (–0.72), 2.55 (–0.628), 2.72 (–0.51), 2.83
(–0.461), 2.93 (–0.412), 3.44 (–0.15), 3.59 (–0.108), 3.80 (–0.035),
4.07 (0.058), 4.20 (0.164), 4.40 (0.214), 4.69 (0.329), 5.07 (0.528),
5.22 (0.572), 5.94 (0.919)
X2 = Cl, X6 = NO2 (1)
3.59 (–0.733), 4.07 (–0.668), 4.20 (–0.554), 4.40 (–0.384), 4.69
(–0.206), 5.07 (–0.237), 5.22 (0.017), 5.46 (0.101), 5.64 (0.158),
5.94 (0.324), 6.13 (0.387), 6.36 (0.53), 6.74 (0.726), 7.42 (1.039)
X2 = Cl, X6 = NO2 (2)
3.59 (–0.78), 4.07 (–0.686), 4.20 (–0.54), 4.40 (–0.394), 4.69
(–0.242), 5.07 (–0.106), 5.22 (–0.023), 5.46 (0.063), 5.64 (0.189),
5.94 (0.32), 6.13 (0.341), 6.36 (0.512), 6.74 (0.692), 7.42 (1.03)
X2 = X4 = Cl,
X6 = NO2 (1)
4.20 (–1.225), 4.69 (–1.112), 5.00 (–0.749), 5.22 (–0.743), 5.46
(–0.652), 5.64 (–0.626), 5.94 (–0.5), 6.13 (–0.359), 6.36 (–0.267),
6.55 (–0.206), 6.74 (–0.078), 6.96 (–0.02), 7.19 (0.129), 7.42
(0.242), 7.57 (0.309), 7.72 (0.375), 8.13 (0.518), 8.48 (0.687), 9.15
(1.03)
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Interconnected Acidity Functions
1645
TABLE I
(Continued)
Substituen tsa
c (log I)
X2 = X4 = Cl,
X6 = NO2 (2)
4.69 (–1), 5.00 (–0.99), 5.22 (–0.777), 5.46 (–0.665), 5.64 (–0.563),
5.94 (–0.43), 6.13 (–0.434), 6.36 (–0.265), 6.55 (–0.207), 6.74
(–0.052), 6.96 (–0.049), 7.19 (0.076), 7.42 (0.137), 7.57 (0.247), 7.72
(0.368), 8.13 (0.452), 8.48 (0.665), 9.15 (1.042)
X2 = X4 = NO2 (1)
6.36 (–1.275), 6.74 (–1.133), 7.42 (–0.895), 7.77 (–0.688), 8.13
(–0.55), 8.48 (–0.355), 8.81 (–0.239), 8.92 (–0.156), 9.02 (–0.081),
9.15 (–0.113), 9.35 (0.065), 9.56 (0.209), 9.70 (0.267), 9.85 (0.349),
10.01 (0.397), 10.17 (0.472), 10.51 (0.7), 10.95 (1.045), 11.44
(1.161)
X2 = X4 = NO2 (2)
X2 = X6 = NO2 (1)
X2 = X6 = NO2 (2)
R = CH3,
7.77 (–0.831), 8.13 (–0.614), 8.48 (–0.398), 8.64 (–0.372), 8.81
(–0.37), 8.92 (–0.217), 9.02 (–0.123), 9.15 (–0.15), 9.35 (0.033), 9.56
(0.179), 9.70 (0.24), 9.85 (0.319), 10.01 (0.381), 10.17 (0.416), 10.51
(0.694), 10.95 (1.034), 11.44 (1.159)
9.85 (–0.898), 10.17 (–0.714), 10.25 (–0.67), 10.32 (–0.423), 10.51
(–0.381), 10.69 (–0.212), 10.73 (–0.208), 10.95 (0.004), 11.19
(0.132), 11.44 (0.172), 11.63 (0.288), 11.73 (0.42), 11.93 (0.619),
12.38 (0.854), 12.60 (1.144)
9.85 (–0.929), 10.17 (–0.785), 10.25 (–0.526), 10.32 (–0.431), 10.51
(–0.431), 10.69 (–0.236), 10.73 (–0.22), 10.95 (0.013), 11.19 (0.113),
11.44 (0.154), 11.63 (0.322), 11.73 (0.397), 11.93 (0.576), 12.38
(0.874), 12.60 (1.16)
0.0310 (–1.075), 0.0413 (–0.711), 0.0470 (–0.443), 0.0789 (–0.146),
X2 = Cl, X6 = NO2 (1) 0.0960 (–0.086), 0.149 (0.084), 0.195 (0.124), 0.243 (0.181), 0.289
(0.28), 0.424 (0.482), 0.516 (0.563), 1.02 (0.967)
R = CH3,
0.0310 (–1.038), 0.0413 (–0.764), 0.0470 (–0.403), 0.0789 (–0.151),
X2 = Cl, X6 = NO2 (2) 0.0960 (–0.178), 0.149 (0.066), 0.195 (0.146), 0.243 (0.2), 0.289
(0.29), 0.424 (0.469), 0.516 (0.519), 1.02 (0.945)
R = CH3,
0.0470 (–0.691), 0.0641 (–0.524), 0.0789 (–0.368), 0.0960 (–0.193),
X2 = Cl, X6 = NO2 (3) 0.149 (–0.041), 0.195 (0.029), 0.243 (0.14), 0.289 (0.265), 0.336
(0.313), 0.424 (0.465), 0.516 (0.552), 0.585 (0.67), 0.784 (0.84), 1.02
(1.094), 2.06 (1.636)
R = CH3,
0.0789 (–0.277), 0.0960 (–0.295), 0.149 (–0.102), 0.195 (0.026),
X2 = Cl, X6 = NO2 (4) 0.243 (0.126), 0.289 (0.23), 0.336 (0.432), 0.424 (0.397), 0.516
(0.605), 0.585 (0.65), 0.784 (0.798), 1.02 (1.021), 2.06 (1.588)
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1646
Pytela, Kulhánek, Jirásková, Nevěčná:
TABLE I
(Continued)
Substituen tsa
c (log I)
R = CH3,
X4 = NO2 (1)
0.0470 (–0.617), 0.0960 (–0.341), 0.131 (–0.228), 0.168 (–0.133), 0.219
(–0.002), 0.271 (0.151), 0.321 (0.249), 0.377 (0.281), 0.424 (0.366),
0.516 (0.471), 0.585 (0.519), 0.681 (0.647), 0.784 (0.728), 0.875 (0.821),
1.02 (0.894), 1.06 (0.912), 1.12 (0.949), 1.14 (0.959)
R = CH3,
X4 = NO2 (2)
0.0470 (–0.566), 0.0960 (–0.317), 0.131 (–0.222), 0.168 (–0.091), 0.219
(0.064), 0.271 (0.19), 0.321 (0.265), 0.377 (0.314), 0.424 (0.36), 0.516
(0.523), 0.585 (0.571), 0.681 (0.673), 0.784 (0.721), 0.875 (0.79), 1.02
(0.905), 1.06 (0.918), 1.12 (0.964), 1.14 (0.983)
R = CH3,
X2 = NO2 (1)
0.219 (–1.148), 0.516 (–0.738), 0.731 (–0.546), 0.828 (–0.413), 1.02
(–0.32), 1.12 (–0.247), 1.21 (–0.187), 1.36 (–0.062), 1.45 (–0.004), 1.52
(0.022), 1.63 (0.115), 1.77 (0.202), 1.91 (0.256), 2.06 (0.348), 2.24
(0.48), 2.42 (0.62), 2.60 (0.727), 2.83 (0.827), 2.93 (0.876), 3.22 (1.062),
4.07 (1.578)
R = CH3,
X2 = NO2 (2)
0.336 (–1.034), 0.424 (–0.881), 0.585 (–0.706), 0.784 (–0.465), 1.02
(–0.292), 1.12 (–0.242), 1.31 (–0.103), 1.58 (0.062), 1.77 (0.187), 1.92
(0.324), 2.24 (0.536), 2.60 (0.713), 2.83 (0.868), 2.93 (0.868), 3.22
(0.985), 3.44 (1.26), 3.59 (1.26), 3.80 (1.371), 4.07 (1.532)
R = CH3,
X2 = NO2 (3)
0.336 (–0.782), 0.424 (–0.686), 0.784 (–0.394), 1.02 (–0.218), 1.12
(–0.112), 1.31 (–0.034), 1.58 (0.085), 1.77 (0.213), 1.92 (0.348), 2.24
(0.548), 2.60 (0.725), 2.83 (0.878), 2.93 (0.933), 3.22 (1.094), 3.44
(1.228), 3.59 (1.301), 3.80 (1.376), 4.07 (1.525)
R = CH3,
X2 = NO2 (4)
0.336 (–0.729), 0.424 (–0.746), 0.784 (–0.383), 1.02 (–0.249), 1.12
(–0.15), 1.31 (–0.042), 1.58 (0.087), 1.77 (0.216), 1.92 (0.372), 2.24
(0.566), 2.60 (0.757), 2.83 (0.888), 2.93 (0.949), 3.22 (1.104), 3.44
(1.242), 3.59 (1.318), 3.80 (1.397), 4.07 (1.507)
R = CH3,
X2 = X6 = NO2
2.24 (–1.162), 2.60 (–0.796), 2.83 (–0.695), 2.93 (–0.681), 3.22 (–0.536),
3.44 (–0.525), 3.59 (–0.554), 3.80 (–0.404), 4.07 (–0.257), 4.20 (–0.235),
4.40 (–0.197), 4.69 (0.022), 5.07 (0.324)
a
Th e n um bers in brackets den ote th e order of repeated m easurem en ts, if an y.
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Interconnected Acidity Functions
1647
TABLE II
Values of log I depen din g on con cen tration of perch loric acid in water for th e studied sub-
stituted derivatives of an ilin e of th e followin g gen eral form ula (th e substituen ts n ot sh own
are h ydrogen s)
NHCH3
X6
X2
X4
Substituen tsa
c (log I)
X2 = Cl, X6 = NO2 (1) 0.0483 (–0.397), 0.0748 (–0.175), 0.0972 (–0.113), 0.120 (0.038),
0.148 (0.185), 0.181 (0.26), 0.214 (0.387), 0.250 (0.414), 0.280
(0.476), 0.328 (0.522), 0.369 (0.655), 0.412 (0.697), 0.566 (0.904),
0.723 (1.056)
X2 = Cl, X6 = NO2 (2) 0.0483 (–0.317), 0.0748 (–0.168), 0.0972 (–0.062), 0.120 (0.01),
0.148 (0.17), 0.181 (0.252), 0.214 (0.362), 0.250 (0.424), 0.280
(0.517), 0.328 (0.568), 0.369 (0.644), 0.412 (0.726), 0.566 (0.939)
X4 = NO2 (1)
X4 = NO2 (2)
X2 = NO2 (1)
0.0154 (–1.223), 0.0337 (–0.833), 0.0748 (–0.523), 0.120 (–0.312),
0.148 (–0.161), 0.181 (–0.081), 0.214 (0.008), 0.250 (0.098), 0.280
(0.191), 0.328 (0.271), 0.412 (0.373), 0.475 (0.513), 0.606 (0.602)
0.0154 (–1.22), 0.0337 (–0.837), 0.0748 (–0.504), 0.120 (–0.317),
0.148 (–0.193), 0.181 (–0.065), 0.214 (0.029), 0.250 (0.094), 0.280
(0.19), 0.328 (0.263), 0.412 (0.379), 0.475 (0.494), 0.606 (0.612)
0.369 (–0.88), 0.566 (–0.649), 0.723 (–0.502), 0.896 (–0.302), 1.06
(–0.247), 1.2 (–0.117), 1.31 (–0.04), 1.39 (0.03), 1.55 (0.089), 1.65
(0.197), 1.76 (0.265), 1.88 (0.31), 2.04 (0.354), 2.15 (0.417), 2.42
(0.553)
X2 = NO2 (2)
0.214 (–1.055), 0.566 (–0.59), 0.723 (–0.494), 0.896 (–0.281), 1.06
(–0.201), 1.2 (–0.069), 1.31 (–0.004), 1.39 (0.069), 1.55 (0.132), 1.65
(0.209), 1.76 (0.275), 1.88 (0.348), 2.04 (0.38), 2.15 (0.471)
a
Th e n um bers in brackets den ote th e order of repeated m easurem en ts, if an y.
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1648
Pytela, Kulhánek, Jirásková, Nevěčná:
TABLE III
Values of log I quan tity depen din g on con cen tration of m eth an esulfon ic acid in water for
th e studied substituted derivatives of an ilin e of th e followin g gen eral form ula (th e substitu-
en ts n ot sh own are h ydrogen s)
NRCH3
X6
X5
X2
X4
Substituen tsa
c (log I)
X2 = X6 = Cl (1)
0.0303 (–1.265), 0.0633 (–0.893), 0.0919 (–0.716), 0.151 (–0.577),
0.249 (–0.281), 0.293 (–0.166), 0.394 (–0.035), 0.508 (0.116), 0.687
(0.254), 0.863 (0.379), 1.37 (0.649), 1.89 (0.832), 2.00 (0.853)
X2 = X6 = Cl (2)
0.0303 (–1.222), 0.0633 (–0.766), 0.0919 (–0.487), 0.151 (–0.417),
0.249 (–0.224), 0.293 (–0.09), 0.394 (0.04), 0.508 (0.169), 0.687
(0.344), 0.863 (0.449), 1.10 (0.556), 1.37 (0.69), 1.89 (0.867), 2.00
(0.891)
X2 = NO2 (1)
0.115 (–0.943), 0.170 (–0.9), 0.249 (–0.75), 0.508 (–0.401), 0.652
(–0.329), 0.721 (–0.292), 0.833 (–0.225), 0.863 (–0.206), 1.03
(–0.113), 1.14 (–0.052), 1.30 (0.035), 1.39 (0.086), 1.54 (0.123),
1.79 (0.245), 2.00 (0.292), 2.29 (0.4), 2.47 (0.45), 2.68 (0.555),
3.02 (0.605), 3.88 (0.922), 4.87 (1.191)
X2 = NO2 (2)
0.249 (–0.98), 0.334 (–0.844), 0.508 (–0.595), 0.652 (–0.38), 0.721
(–0.275), 0.833 (–0.267), 1.03 (–0.173), 1.14 (–0.102), 1.30
(–0.023), 1.39 (0.042), 1.54 (0.096), 1.79 (0.194), 2.00 (0.254), 2.29
(0.36), 2.47 (0.436), 2.68 (0.52), 3.02 (0.583), 3.88 (0.854), 4.87
(1.15)
X2 = CH3O, X6 = NO2
0.550 (–0.746), 1.03 (–0.376), 1.30 (–0.2), 2.29 (0.123), 4.21
(0.721), 5.19 (1.03), 6.16 (1.405)
X2 = CH3, X6 = NO2 (1) 0.356 (–1.128), 0.550 (–0.896), 0.687 (–0.734), 0.863 (–0.669), 1.05
(–0.544), 1.26 (–0.439), 1.47 (–0.385), 1.64 (–0.27), 1.89 (–0.187),
2.08 (–0.127), 2.29 (–0.042), 2.47 (0.027), 2.68 (0.132), 2.86 (0.16),
3.02 (0.202), 3.33 (0.292), 3.62 (0.404), 3.88 (0.474), 4.36 (0.614),
4.87 (0.767), 5.19 (0.867), 6.16 (1.184)
X2 = CH3, X6 = NO2 (2) 0.201 (–1.408), 0.356 (–1.204), 0.550 (–0.872), 0.687 (–0.771),
0.863 (–0.696), 1.05 (–0.507), 1.26 (–0.424), 1.47 (–0.377), 1.64
(–0.279), 1.89 (–0.143), 2.08 (–0.075), 2.29 (–0.037), 2.47 (0.05),
2.68 (0.142), 2.86 (0.166), 3.02 (0.193), 3.33 (0.286), 3.62 (0.402),
3.88 (0.478), 4.36 (0.603), 4.87 (0.761), 5.19 (0.883), 6.16 (1.198)
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Interconnected Acidity Functions
1649
TABLE III
(Continued)
Substituen tsa
c (log I)
X2 = NO2, X4 = Cl (1)
0.652 (–1.291), 1.14 (–0.93), 1.39 (–0.758), 2.00 (–0.435), 2.29
(–0.438), 2.86 (–0.235), 3.33 (–0.098), 3.62 (0.02), 3.88 (0.066),
4.21 (0.151), 4.87 (0.387), 4.97 (0.413), 5.19 (0.468), 5.58
(0.578), 5.80 (0.758), 6.51 (0.936), 7.17 (1.197), 7.72 (1.329),
8.04 (1.571)
X2 = NO2, X4 = Cl (2)
0.652 (–1.249), 1.14 (–0.823), 1.39 (–0.763), 2.00 (–0.512), 2.29
(–0.41), 2.86 (–0.232), 3.33 (–0.104), 3.62 (0.027), 3.88 (0.057),
4.21 (0.169), 4.87 (0.364), 4.97 (0.416), 5.19 (0.488), 5.58
(0.551), 5.80 (0.74), 6.51 (0.907), 7.17 (1.18), 7.72 (1.316), 8.04
(1.487)
X2 = X5 = Cl, X4 = NO2 (1) 3.49 (–1.03), 4.21 (–0.784), 4.97 (–0.549), 5.42 (–0.386), 5.58
(–0.318), 5.80 (–0.245), 6.00 (–0.16), 6.29 (–0.074), 6.51
(0.016), 6.68 (0.18), 6.96 (0.169), 7.17 (0.266), 7.55 (0.411),
8.04 (0.585), 8.46 (0.727), 8.65 (0.843), 8.90 (1.063), 9.19
(1.231), 9.86 (1.326)
X2 = X5 = Cl, X4 = NO2 (2) 2.68 (–1.194), 3.49 (–0.999), 4.21 (–0.704), 4.97 (–0.539), 5.42
(–0.362), 5.58 (–0.307), 5.80 (–0.207), 6.00 (–0.133), 6.29
(–0.067), 6.51 (0.008), 6.68 (0.172), 6.96 (0.146), 7.17 (0.26),
7.55 (0.398), 8.04 (0.499), 8.90 (1.056), 9.86 (1.33)
X2 = Cl, X6 = NO2 (1)
5.58 (–0.858), 6.05 (–0.785), 6.51 (–0.566), 6.96 (–0.524), 7.17
(–0.406), 7.39 (–0.272), 7.55 (–0.226), 7.72 (–0.13), 8.04
(–0.055), 8.25 (–0.028), 8.46 (0.069), 8.65 (0.247), 8.83 (0.246),
9.00 (0.335), 9.19 (0.444), 9.43 (0.535), 9.77 (0.697), 10.08
(0.92), 10.36 (1.159)
X2 = Cl, X6 = NO2 (2)
5.58 (–1.012), 6.05 (–0.772), 6.51 (–0.61), 6.96 (–0.434), 7.17
(–0.435), 7.39 (–0.322), 7.55 (–0.244), 7.72 (–0.146), 8.04
(–0.096), 8.25 (–0.024), 8.46 (0.091), 8.65 (0.226), 8.83 (0.255),
9.00 (0.327), 9.19 (0.452), 9.43 (0.56), 9.77 (0.755), 10.08
(0.965), 10.36 (1.188)
X2 = X4 = Cl, X6 = NO2 (1) 6.16 (–1.345), 7.39 (–1.137), 8.13 (–0.896), 8.46 (–0.764), 8.65
(–0.583), 8.90 (–0.504), 9.19 (–0.358), 9.35 (–0.264), 9.43
(–0.202), 9.68 (–0.14), 9.86 (–0.024), 9.97 (0.056), 10.08
(0.105), 10.17 (0.219), 10.36 (0.342), 10.61 (0.368), 11.00
(0.767), 11.91 (1.105)
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1650
Pytela, Kulhánek, Jirásková, Nevěčná:
TABLE III
(Continued)
Substituen tsa
c (log I)
X2 = X4 = Cl, X6 = NO2 (2) 7.39 (–1.235), 8.13 (–0.916), 8.46 (–0.789), 8.65 (–0.582), 8.90
(–0.467), 9.19 (–0.392), 9.35 (–0.281), 9.43 (–0.226), 9.68
(–0.152), 9.86 (–0.016), 9.97 (0.05), 10.08 (0.105), 10.17
(0.198), 10.36 (0.33), 10.61 (0.336), 11.00 (0.767), 11.91 (1.084)
X2 = X4 = NO2 (1)
9.86 (–0.822), 10.08 (–0.739), 10.36 (–0.426), 10.48 (–0.474),
10.61 (–0.42), 10.72 (–0.32), 10.83 (–0.126), 11.00 (–0.065),
11.26 (–0.013), 11.58 (0.143), 11.64 (0.233), 11.80 (0.189),
11.91 (0.249), 12.25 (0.592), 12.41 (0.595)
X2 = X4 = NO2 (2)
9.43 (–1.195), 9.86 (–0.976), 10.08 (–0.712), 10.48 (–0.526),
10.61 (–0.491), 10.72 (–0.347), 10.83 (–0.186), 11.00 (–0.014),
11.26 (0.053), 11.58 (0.142), 11.64 (0.206), 11.80 (0.214), 11.91
(0.23), 12.10 (0.47), 12.25 (0.576), 12.41 (0.697), 13.00 (0.934),
13.28 (1.37)
X2 = X4 = NO2 (3)
X2 = X6 = NO2 (1)
9.43 (–1.321), 10.08 (–0.752), 10.36 (–0.49), 10.83 (–0.11),
11.00 (–0.05), 11.26 (0), 11.80 (0.195), 11.91 (0.263), 12.41
(0.702), 13.00 (0.944)
11.91 (–0.692), 12.25 (–0.427), 12.41 (–0.364), 12.51 (–0.362),
12.61 (–0.272), 12.80 (–0.059), 13.00 (0.055), 13.06 (0.146),
13.14 (0.141), 13.20 (0.227), 13.28 (0.671), 13.59 (0.809), 13.90
(0.949), 14.20 (1.231)
X2 = X6 = NO2 (2)
11.91 (–0.72), 12.25 (–0.592), 12.41 (–0.301), 12.51 (–0.322),
12.61 (–0.222), 12.80 (–0.082), 13.00 (0.068), 13.06 (0.058),
13.14 (0.139), 13.20 (0.183), 13.28 (0.636), 13.59 (0.776), 13.90
(0.936), 14.20 (1.16)
X2 = X6 = NO2 (3)
10.36 (–1.787), 10.83 (–1.26), 11.00 (–1.085), 11.26 (–1.046),
11.64 (–0.84), 11.91 (–0.797), 12.25 (–0.315), 13.00 (0.069),
13.28 (0.596)
R = CH3,
0.0210 (0.428), 0.0303 (0.673), 0.0633 (1.02), 0.151 (1.544)
X2 = CH3O, X6 = NO2
R = CH3,
X2 = Cl, X6 = NO2 (1)
0.0210 (–0.892), 0.0303 (–0.659), 0.0409 (–0.557), 0.0491
(–0.451), 0.0633 (–0.339), 0.0767 (–0.22), 0.0919 (–0.157),
0.115 (–0.046), 0.151 (0.077), 0.201 (0.241), 0.249 (0.304),
0.293 (0.377), 0.394 (0.53), 0.508 (0.685), 0.687 (0.823), 0.863
(0.933), 1.37 (1.265), 1.89 (1.407)
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Interconnected Acidity Functions
1651
TABLE III
(Continued)
Substituen tsa
c (log I)
R = CH3,
0.0210 (–0.868), 0.0303 (–0.648), 0.0409 (–0.627), 0.0491 (–0.393),
X2 = Cl, X6 = NO2 (2) 0.0633 (–0.269), 0.0767 (–0.167), 0.0919 (–0.054), 0.115 (0.073),
0.201 (0.192), 0.249 (0.318), 0.293 (0.384), 0.394 (0.542), 0.508
(0.677), 0.687 (0.834), 0.863 (0.941), 1.37 (1.136), 1.89 (1.382)
R = CH3,
X4 = NO2
0.863 (0.554), 1.89 (1.08), 2.86 (1.528), 3.88 (1.792)
R = CH3,
X2 = NO2
0.863 (–0.642), 1.89 (–0.091), 2.86 (0.196), 3.88 (0.594), 5.19
(1.024), 6.16 (1.445)
R = CH3,
X2 = X6 = NO2 (1)
6.00 (–0.582), 6.51 (–0.361), 6.68 (–0.172), 6.82 (–0.125), 6.96
(–0.145), 7.17 (–0.088), 7.39 (0.037), 7.72 (0.272), 8.04 (0.398), 8.13
(0.419), 8.39 (0.575), 8.46 (0.541), 8.65 (0.731), 8.90 (0.955), 9.05
(0.953), 9.19 (0.946), 9.86 (1.327)
R = CH3,
X2 = X6 = NO2 (2)
4.21 (–1.048), 4.87 (–0.86), 5.42 (–0.619), 5.58 (–0.562), 5.80
(–0.549), 6.00 (–0.438), 6.29 (–0.372), 6.51 (–0.237), 6.68 (–0.069),
6.82 (–0.044), 6.96 (–0.054), 7.17 (0.026), 7.39 (0.121), 7.72 (0.343),
8.04 (0.43), 8.13 (0.481), 8.39 (0.608), 8.46 (0.604), 8.65 (0.774),
8.90 (1.003), 9.05 (0.963), 9.19 (0.955), 9.86 (1.418)
a
Th e n um bers in brackets den ote th e order of repeated m easurem en ts, if an y.
Th e statistical h ypoth eses of in tercept equal zero (ttest = 1.264, t0.95(67) =
1.996) an d un it slope (ttest = 1.963, t0.95(67) = 1.996) in Eq. (1) were n ot re-
jected. Th erefrom it follows th at th e acidity fun ction obtain ed by us an d
th ose given in literature are iden tical with in experim en tal error. Th e rela-
tion sh ip between our acidity fun ction an d th at of ref.24 for perch loric acid
is given by Eq. (3).
H0(HClO4) = (0.116 ± 0.031) + (0.955 ± 0.009) H0(HClO4, ref.24)
s = 0.75, r = 0.998, n = 52
(3)
In th is case, th e statistical h ypoth eses of in tercept equal zero (ttest = 4.82,
0.95(50) = 2.009) an d un it slope (ttest = 38.1, t0.95(50) = 2.009) were rejected.
t
Th e agreem en t between th e two fun ction s is worse in th is case, th e differ-
en ces bein g caused by sm all deviation s in th e course of th e two acidity
fun ction s, particularly th ose in th e m iddle of th e con cen tration in terval.
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1652
Pytela, Kulhánek, Jirásková, Nevěčná:
TABLE IV
Values of acidity fun ction s H0 depen din g on con cen tration c (in m ol dm –3) of sulfuric,
perch loric, an d m eth an esulfon ic acid in water
c
H0(H2SO4) H0(HClO4) H0(CH3SO3H)
c
H0(H2SO4) H0(HClO4) H0(CH3SO3H)
0.02
0.04
0.06
0.08
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.60
0.70
0.80
0.90
1.00
1.2
1.690
3.4
3.6
3.8
4.0
4.2
4.4
4.6
4.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.4
6.6
6.8
7.0
7.2
7.4
7.6
7.8
8.0
8.2
8.4
8.6
8.8
9.0
–1.607
–1.743
–1.856
–1.936
–2.006
–2.129
–2.242
–2.349
–2.448
–2.528
–2.622
–2.733
–2.820
–2.900
–2.989
–3.083
–3.194
–3.273
–3.343
–3.475
–3.545
–3.621
–3.682
–3.766
–3.861
–3.933
–3.998
–4.082
–4.239
–1.590
–1.690
–1.832
–1.938
–2.071
–2.188
–2.308
–2.410
–2.483
–2.589
–2.695
–2.789
–2.913
–3.008
–3.113
–3.234
–3.342
–3.433
–3.526
–3.643
–3.796
–3.971
–4.156
–4.245
–4.358
–4.456
–4.568
–4.798
–4.963
–0.964
–1.071
–1.142
–1.161
–1.192
–1.279
–1.353
–1.412
–1.462
–1.522
–1.569
–1.633
–1.686
–1.726
–1.894
–1.916
–1.978
–2.055
–2.112
–2.169
–2.233
–2.355
–2.462
–2.510
–2.546
–2.665
–2.741
–2.882
–2.983
1.494
1.264
1.324
1.173
1.456
1.179
1.083
1.066
1.036
1.012
0.966
0.885
0.811
0.765
0.762
0.672
0.599
0.616
0.561
0.508
0.557
0.448
0.387
0.511
0.351
0.326
0.448
0.302
0.257
0.316
0.247
0.173
0.247
0.206
0.096
0.214
0.098
0.023
0.146
–0.045
–0.096
–0.209
–0.229
–0.384
–0.496
–0.600
–0.721
–0.840
–1.007
–1.059
–1.202
–1.318
–1.377
–1.470
–0.053
–0.116
–0.211
–0.280
–0.415
–0.530
–0.647
–0.767
–0.837
–0.949
–1.059
–1.178
–1.260
–1.364
–1.484
0.038
–0.023
–0.040
–0.097
–0.238
–0.340
–0.417
–0.501
–0.549
–0.641
–0.702
–0.776
–0.829
–0.875
–0.917
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Interconnected Acidity Functions
1653
TABLE IV
(Continued)
c
H0(H2SO4) H0(HClO4) H0(CH3SO3H)
c
H0(H2SO4) H0(HClO4) H0(CH3SO3H)
9.2
9.4
–4.329
–4.431
–4.558
–4.602
–4.676
–4.748
–4.983
–5.058
–5.270
–5.396
–5.475
–5.538
–5.640
–5.073
–5.209
–5.447
–5.700
–5.955
–6.106
–6.250
–3.056
–3.104
–3.149
–3.354
–3.470
–3.624
–3.764
–3.843
–4.139
–4.251
–4.310
–4.409
–4.527
11.8
12.0
12.2
12.4
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
–5.849
–6.001
–6.146
–6.312
–6.528
–4.570
–4.643
–4.895
–5.008
–5.120
–5.307
–5.399
–5.693
–6.011
–6.115
–6.270
–6.422
9.6
9.8
10.0
10.2
10.4
10.6
10.8
11.0
11.2
11.4
11.6
6
5
4
H
0
3
2
1
0
–1
0
4
8
12
c
acid
FIG. 1
Depen den ce of con structed acidity fun ction s H0 in sulfuric acid (❍), perch loric acid (❍), an d
m eth an esulfon ic acid (∆) on th e con cen tration of acid cacid in m ol dm –3
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1654
Pytela, Kulhánek, Jirásková, Nevěčná:
Th e agreem en t of th e con structed acidity fun ction in m eth an esulfon ic
acid can n ot be verified because correspon din g literature data are n ot avail-
able.
With regard to th e fact th at our acidity fun ction s an d th ose taken from
literature were con structed on differen t experim en tal data, an d th e agree-
m en t with th e m ore or less stan dard acidity fun ction in sulfuric acid is very
good, it is possible to claim th at th e suggested algorith m is correct.
Th e relation sh ip between our acidity fun ction s con structed in sulfuric
an d perch loric acids an d th e scale of th e gen eralised fun ction X (ref.6) is ex-
pressed by Eqs (4) an d (5).
H0(H2SO4) = (0.047 ± 0.0118) + (1.136 ± 0.034) log cH + + (0.990 ± 0.012) X
s = 0.06, r = 0.9997, n = 28
(4)
H0(HClO4) = (0.123 ± 0.026) + (0.970 ± 0.052) log cH + + (0.951 ± 0.018) X
s = 0.08, r = 0.9993, n = 26 (5)
In an alogy to Eqs (2) an d (3), also in th is case th e fit is very close (th e resid-
ual stan dard deviation bein g com parable with th e accuracy of m easure-
m en ts), wh ich con firm s both th e correctn ess of th e algorith m suggested
an d validity of th e “excess acidity” prin ciple as well as correctn ess of adjust-
m en t of th e scale of X values.
In order to evaluate m utual sim ilarity of th e acidity fun ction calculated,
th e values of Table IV were subm itted to prin cipal com pon en t an alysis
(PCA). Th e first laten t variable ch aracterisin g com m on properties of an a-
lysed acidity fun ction s described 99.67% of th eir variability. Th is value is
relatively h igh an d in dicates a h igh exten t of m utual sim ilarity of th ese
acidity fun ction s irrespective of differen t con cen tration scales an d th e fact
th at on e of th e acids is dibasic an d th e oth er two are m on obasic. From
Fig. 1 an d from values of loadin g p in sulfuric acid (p = 4.505), perch loric
acid (p = 5.443), an d m eth an esulfon ic acid (p = 3.816) obtain ed by PCA, it
follows th at (in accordan ce with ref.2) th e steepn ess of th e acidity fun ction
in perch loric acid is greater th an th at in sulfuric acid. Th e steepn ess of th e
acidity fun ction in th e weakest acid (m eth an esulfon ic acid) is th e lowest in
th is case.
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Interconnected Acidity Functions
1655
pKa Values of Indicators
Th e pKa values calculated accordin g to th e above-given algorith m from th e
data publish ed in a previous paper27 an d th ose given in Tables I–III, an d th e
pKa values taken from literature are sum m arised in Table V. Th e literature
an d th e calculated values are com pared graph ically in Fig. 2. Th e poin ts are
fitted with a regression straigh t lin e, wh ich docum en ts both relation s be-
tween th e in dividual values an d varian ce of th e pKa values publish ed in lit-
erature. As it can be seen in Fig. 2, th e agreem en t between th e pKa values
calculated an d th ose publish ed in literature is very good.
Validity of the Algorithm Suggested
Th e validity of th e algorith m suggested is con sidered to be verified by com -
parison of th e acidity fun ction s (Eqs (2)–(5)) an d th e pKa values obtain ed by
th is algorith m with reliable literature data (Table V, Fig. 2). With respect to
th e fact th at th e calculation s were based on differen t experim en tal data an d
differen t calculation procedures an d th e results agree well with literature,
th e algorith m suggested for calculatin g th e boun d acidity fun ction s can be
con sidered to be correct.
1
pK (ref.)
a
0
–1
–2
–3
–4
–5
–5
–4
–3
–2
–1
0
pK
a
FIG. 2
Depen den ce of th e pKa values taken from literature an d th ose calculated accordin g to th e
suggested algorith m (Table V). Th e straigh t lin e was calculated by regression
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1656
Pytela, Kulhánek, Jirásková, Nevěčná:
TABLE V
Com parison of calculated pKa values an d th eir stan dard deviation s spK of substituted an i-
lin es an d N-m eth ylan ilin es with correspon din g literature data
In dicator
pKa (spK
)
pKa, referen ce
2,6-Dich loroan ilin e
0.353
0.40a (H2SO4)
(0.068)
2-Nitroan ilin e
–0.300
(0.053)
–0.25b (H2SO4), –0.29e (H2SO4),
–0.33f (H2SO4), –0.30g (H2SO4),
–0.35h (H2SO4), 0.10a (HClO4),
–0.31b (HClO4), –0.29i (HClO4),
–0.28j (HClO4), –0.29b (HCl), –0.31k (HCl),
–0.32b (HNO3), –0.22b (H3PO4),
–0.13d (CF3CO2H), –0,24d (CCl3CO2H),
–0.27c (Mc)
2-Meth oxy-6-n itroan ilin e
2-Meth yl-6-n itroan ilin e
4-Ch loro-2-n itroan ilin e
–0.481
(0.040)
–0.694
(0.036)
–1.076
(0.067)
–0.97b (H2SO4),
–1.02e (H2SO4), –1.06g (H2SO4),
–0.97h (H2SO4), –0.62a (HClO4),
–1.03b (HClO4), –1.07i (HClO4), –1.03b (HCl),
–1.09k (HCl), –1.09b (HNO3), –1.01b (H3PO4),
–0.94d (CF3CO2H), –1.05c (Mc)
2,5-Dich loro-4-n itroan ilin e
2-Ch loro-6-n itroan ilin e
–1.913
(0.073)
–1.90f (H2SO4), –1.75g (H2SO4),
–1.74h (H2SO4), –1.79i (HClO4),
–1.78j (HClO4), –1.82k (HCl),
–1.80c (Mc)
–2.569
(0.047)
–2.54f (H2SO4), –2.38g (H2SO4), –2.60c (Mc)
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Interconnected Acidity Functions
1657
TABLE V
(Continued)
In dicator
pKa (spK
)
pKa, referen ce
2,4-Dich lor-6-n itroan ilin e
–3.347
(0.072)
–3.34b (H2SO4),
–3.28f (H2SO4), –3.01h (H2SO4),
–3.30b (HClO4),
–3.00j (HClO4), –3.27k (HCl), –3.10b (H3PO4),
–3.50c (Mc)
2,4-Din itroan ilin e
–4.358
(0.064)
–4.14a (H2SO4), –4.50b (H2SO4),
–4.45f (H2SO4), –4.27g (H2SO4),
–4.27h (H2SO4), –4.55b (HClO4),
–4.26i (HClO4), –4.25j (HClO4), –5.25c (Mc)
2,6-Din itroan ilin e
–5.375
(0.061)
–5.64f (H2SO4), –5.39g (H2SO4),
–5.37h (H2SO4), –5.25i (HClO4),
–5.23j (HClO4),
–5.90c (Mc)
N-Meth yl-2-m eth oxy-6-
2.227
n itroan ilin e
(0.061)
N-Meth yl-2-ch loro-6-
0.841
n itroan ilin e
(0.084)
N-Meth yl-4-n itroan ilin e
N-Meth yl-2-n itroan ilin e
N-Meth yl-2,6-din itroan ilin e
0.633
0.90l , 0.53m
(0.047)
–0.492
(0.060)
–2.141
(0.098)
–2.04a (H2SO4)
a
b
n
c
d
e
f
h
i
j
k
l
Ref.35
ref.42
,
,
ref.4, ref.15
,
ref.36
,
ref.37
,
ref.38
,
g ref.34
,
ref.25
,
ref.24
,
ref.39
,
ref.40 ref.41
, ,
m
ref.43
.
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1658
Pytela, Kulhánek, Jirásková, Nevěčná:
This work was supported by the Grant Agency of Czech Republic (grant No. 203-97-P095).
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Collect. Czech. Chem. Commun. (Vol. 66) (2001)